It is known that measurements of operating parameters of a tire of a wheel of a vehicle are performed by sensors mounted in electronic housings, so-called “wheel unit”, of a system for checking the pressure of the tires, of the type known by the name “TPMS” (initials standing for “Tyre Pressure Monitoring System”).
In a known manner, the wheel units comprise, generally, a microprocessor, a memory, a radiofrequency emitter, a power supply battery and at least one radial acceleration sensor able to measure the radial accelerations of the wheel and mounted on a support (forming a printed circuit or “PCB” standing for “Printed Circuit Board”). In the present disclosure, the expression “electronic unit 10” refers to the assembly formed by the radial acceleration sensor and the support of a wheel unit.
A first mode of integration of such an electronic unit into a wheel is represented in FIG. 1A. In FIG. 1A, an electronic unit 10 is mounted on a rim 21 of a wheel 20. The wheel 20 is configured to rotate about a rolling axis. The electronic unit 10 comprises a radial acceleration sensor 12 which measures the radial acceleration that it undergoes over a wheel revolution when the wheel 20 rotates in the direction of rotation illustrated by the arrow 30 around the rolling axis, for example at the positions A1, A2, A3 and A4 such as illustrated in FIGS. 1A and 1B. These measurements are preferentially carried out at fixed frequency.
According to FIG. 1A, the electronic unit 10 therefore also comprises a support 11 forming a printed circuit on which the radial acceleration sensor 12 is mounted. As illustrated in FIG. 1A, the support 11 is mounted on the rim 21 tangentially and parallel to the rolling axis of the wheel 20. The radial acceleration sensor 12 is mounted on the support 11, and measures the accelerations perpendicular to the rolling axis of the wheel 20. This first mode of integration of the electronic unit 10 makes it possible to measure the radial acceleration of the wheel 20 when the vehicle is moving. This radial acceleration is the resultant of two radial components, namely a first component which corresponds to the projection of the gravitational acceleration in the direction of measurement of the radial acceleration sensor 12 and a second component which corresponds to the centrifugal acceleration in the same direction of measurement of the radial acceleration sensor 12.
On the basis of the radial acceleration measurements, it is possible to draw a curve Acc(t) of acceleration as a function of time as illustrated in FIG. 1B. This curve Acc(t) is a sinusoid whose minimum MIN corresponds to the positioning of the radial acceleration sensor 12 in position A1 at 0 degrees with respect to the top of the rim and the maximum MAX corresponds to the positioning of the radial acceleration sensor 12 in position A3 at 180 degrees with respect to the top of the rim.
A numerical processing of these radial acceleration measurements by a processor (not represented) of the electronic unit 10 makes it possible to determine the value MIN of the radial acceleration and therefore the transit of the radial acceleration sensor 12 at the position A1 and/or the value MAX of the radial acceleration and therefore the transit of the radial acceleration sensor 12 at the position A3.
On the basis of these radial acceleration measurement data, it is therefore possible, through appropriate numerical processing, to ascertain the transit of the wheel unit and consequently of the electronic unit 10 at the positions A1 and/or A3 on the wheel 20.
A second mode of integration of such an electronic unit in a wheel is represented in FIG. 2. In FIG. 2, the electronic unit 10 is also mounted on the rim 21 of the wheel 20. The electronic unit 10 comprises a radial acceleration sensor 12 which measures the radial acceleration over a wheel revolution when the wheel 20 rotates in the direction of rotation illustrated by the arrow 30 around the rolling axis such as described previously. According to FIG. 2, the electronic unit 10 also comprises a support 11 forming a printed circuit on which the radial acceleration sensor 12 is mounted. As illustrated in FIG. 2, the support 11 is mounted on the rim 21 in a radial plane of the wheel 20, that is to say a plane containing the rolling axis of the wheel 20. The radial acceleration sensor 12 is mounted perpendicular to the plane of the support 11, that is to say in a manner perpendicular to the plane containing the rolling axis of the wheel 20. This second mode of integration of the electronic unit 10 also makes it possible to measure the radial acceleration of the wheel 20 such as described previously, when the vehicle is moving.
On the basis of the radial acceleration measurements, it is also possible to draw, as a function of the time, the acceleration curve Acc(t) of FIG. 1B.
In the two previous modes of integration of the electronic unit 10 according to FIGS. 1A, 1B and 2, it is noted that the radial acceleration sensor 12 is mounted perpendicular to the plane of the rim 21, the plane of the rim 21 corresponding to the plane of FIGS. 1A and 2, that is to say a plane perpendicular to the rolling axis of the wheel 20. This implies that each mode of integration of the electronic unit 10 requires a specific arrangement of the radial acceleration sensor 12 with respect to the support 11. Indeed, in the first mode of integration the radial acceleration sensor 12 is mounted parallel to the support 11, while in the second mode of integration the radial acceleration sensor 12 is mounted perpendicular to the support 11.
In order to be able to cover the two previous modes of integration of the electronic unit 10 according to FIGS. 1A, 1B and 2, it is necessary to have two different arrangements of electronic unit, each being specifically suitable for a mode of integration of the electronic unit 10 in the wheel 20. It is therefore not possible to use a single arrangement of electronic unit 10 which makes it possible to cover the two previous modes of arrangement of the electronic unit 10 in the wheel 20.
This drawback is particularly inconvenient since it is expensive and it limits the choices of integration of an electronic unit when it is desired to reduce the costs related to the wheel units present in a vehicle.